A user has "Full control" permission on SharePoint Library; when using the Windows Explorer view or a mapped network drive led to Access Denied error. Added site to the Trusted sites list but still getting Access Denied error and to add the site to trusted sites list.
Authenticate to Office 365:
Check the status of the WebClient service:
To keep the connection after you restart the computer, make sure that the WebClient service is running.
More information for your reference:
Mapping a network drive uses WebDav, an older technology which is slower and less reliable than syncing SharePoint files with the new OneDrive sync client. The OneDrive sync client provides Files On-Demand, which allows you to access all your files in OneDrive without using local storage space.